import math
x1,y1,x2,y2=map(float,input().split(' '))

res=math.sqrt((x1-x2)**2+(y1-y2)**2)
print(res)
 import math math x1,y1,x2,y2=map(float,input().split(' ')) x1 map(float,input().split(' ')) map float input().split(' ') ().split () input split ' ' y1 x2 y2 res=math.sqrt((x1-x2)**2+(y1-y2)**2) res math.sqrt((x1-x2)**2+(y1-y2)**2) math.sqrt math sqrt (x1-x2)**2+(y1-y2)**2 (x1-x2)**2 x1-x2 x1 x2 2 (y1-y2)**2 y1-y2 y1 y2 2 print(res) print res x1,y1,x2,y2=map(float,input().split(' ')) map(float,input().split(' ')) x1 res=math.sqrt((x1-x2)**2+(y1-y2)**2) math.sqrt((x1-x2)**2+(y1-y2)**2) res y1,x2,y2=map(float,input().split(' ')) map(float,input().split(' ')) y1 y2=map(float,input().split(' ')) map(float,input().split(' ')) y2 x2,y2=map(float,input().split(' ')) map(float,input().split(' ')) x2
import math
x1,y1,x2,y2=map(float,input().split(' '))

res=math.sqrt((x1-x2)**2+(y1-y2)**2)
print(res)

